import sys
from itertools import combinations
readline = sys.stdin.readline
n = int(readline())
d = sorted(map(int, readline().split()))
x, y = map(int, readline().split())
l = abs(x) + abs(y)
ans = -1
if l == 0:
    ans = 0
elif l in d:
    ans = 1
elif l%2==0:
    if max(d)*2 >= l:
        ans = 2
else:
    d1 = [x for x in d if x % 2 == 0]
    d2 = [x for x in d if x % 2 == 1]
    if d1 != []:
        for a in d2:
            low = 0
            high = len(d1) - 1
            while low < high:
                mid = (high+low) >> 1
                if a + d1[mid] >= l:
                    high = mid
                else:
                    low = mid + 1
            if a + d1[low] < l:
                continue
            b = low
            low = 0
            high = len(d1) - 1
            while low < high:
                mid = (high + low + 1) >> 1
                if a > d1[mid] or abs(a - d1[mid]) <= l:
                    low = mid
                else:
                    high = mid - 1
            if abs(a - d1[low]) > l:
                continue
            c = low
            if b <= c:
                ans = 2
print(ans)